Leafy Longings

Welwitschia, a male plant showing the hatchet-shaped stem, the two splayed leaves, and the temporary cone-bearing branches.

When it comes to sex, Botany has its own expectations. Plants normally include male and female parts in the same individual, commonly even in the same flower. In fact, flowers that bear both anthers (male) and ovaries (female) are so standard as to be called “perfect,” while lacking one or the other makes a flower “imperfect.” Botanists more pointedly apply special terms when things are not so standard.

When the same plant forms separate pollen-producing and egg-producing flowers (imperfect flowers), we say that plant is ‘monoecious’, a term based on the same root as ecology, i.e. oeco Latin/oikos Greek = home. Male and female flowers of monoecious plants share the same home; that is, they are formed on the same individual plant. Corn is monoecious, producing pollen in tassels at the top, and ovaries on cobs along the stem. Begonias also.

Welwitschia, female cones on their branched stems
Welwitschia female, mature cones with pollination droplet

But many kinds of plants are more chaste, forming male flowers on one plant and female flowers on another. These plants are said to have two households, thus we call them “dioecious.” And though I’ve discussed flowering plants up to this moment, reproductive strategies are not limited to the Angiosperms (the flowering plants). Cone-bearing plants show can be either monoecious or dioecious. Among the great plant stories of unisexuality is the predicament of Welwitschia, an unrepentantly dioecious, non-flowering plant.

Welwitschia, male cones on their branched stems

Welwitschia has been around a long time, a curious isolate in its own clade (branch) of the plant kingdom. It’s a rare, vestigial sort, a cone-producing, seed-bearing plant growing in the harsh, narrowly circumscribed sandy coastal region of Namibia (and adjacent Angola). Individual plants hold their own, ornamenting the desert sands as seemingly-molten mounds of foliage.

Its singular habit involves producing a short, slowly broadening stem, extensive roots, and ribbons of leaf that grow from the base in a Rapunzel dynamic. At germination, we are told, two seed leaves (cotyledons) emerge, constituting the only leaves the plant will make. Those two leaves pump out new blade from the base, growing wider as the stem enlarges, splitting into separate ribbons at some point, yet growing patiently. Plants seem capable of surviving hundreds of years, living off meagre water from coastal fogs and sunlight that powers photosynthesis in its long-lived leaves. In protected circumstances (such as a greenhouse) the leaves stretch over a meter in length, but in windblown deserts of its native habitat, leaf blades are shortened, with parched and eroded tips.

This wonderfully bizarrely long-leaved plant harbors many mysteries, and has provoked study since first discovered in 1859 by Friedrich Welwitsch, in Angola. Even plants in the Huntington collection have been brought to the bench, as Michael Frohlich worked with CalTech’s Elliot Meyerowitz in extracting the Welwitschia LEAFY gene to compare the instructions in this ancient plant to genetics of more recent flowering plants.

Michael W. Frohlich and Elliot M. Meyerowitz, “The Search for Flower Homeotic Gene Homologs in Basal Angiosperms and Gnetales: A Potential New source of Data on the Evolutionary Origin of Flowers”, 1997. https://www.journals.uchicago.edu/doi/pdfplus/10.1086/297513

Search the web to find many wonderful articles, with great photos in situ. For example:


Leave a comment

Leave a Reply

%d bloggers like this: